Patent publication 1 discloses a vehicle door handle used in an electronic key system for locking and unlocking a vehicle door in response to a portable device carried by a user. The vehicle door handle disclosed in patent document 1 accommodates a transmission antenna for communicating with the portable device and a sensor electrode for detecting the user approaching the vehicle door based on a change in capacitance. The transmission antenna includes a core and a coil, which is formed by winding conductive wire around the core. The coil is connected to a transmission drive circuit, which transmits a transmission request signal from the transmission antenna. The sensor electrode is accommodated in the door handle and exposed from the door handle so as to face an outside panel of the vehicle door. The sensor electrode is also connected to a capacitance detector, which detects changes in the capacitance between the sensor electrode and the outside panel.
The user approaches the vehicle and first puts his or her hand on the door handle when opening the vehicle door. Therefore, it is desirable that the transmission antenna and the sensor electrode be arranged inside the door handle to achieve the functions of the electronic key system.
The door handle does not accommodate only the transmission antenna and the sensor electrode, and the space inside the door handle is not large. In order to accommodate a plurality of components in the door handle, the door handle must be enlarged. Otherwise, limitations are applied to the shape of the door handle in accordance with the shapes of the components accommodated in the door handle. Therefore, it is desirable that the number of components accommodated in the door handle be reduced.
One method for reducing the number of components incorporated in the door handle would be to use the core of the antenna as the sensor electrode. In this case, the core used as the sensor electrode must be electrically connected to the capacitance detector by, for example, conductive wire. However, it is difficult to connect the conductive wire, which extends from the capacitance detector, to the core. Furthermore, it is desirable that a waterproof structure be provided for a connection point between the core and the conductive wire. However, such a waterproof structure would increase the manufacturing cost.
Patent Publication 1: Japanese Laid-Open Patent Publication No. 2003-13628